Nahita 903 Serie Manual De Instrucciones página 22

Being:
"S=100.0"; value of the slope in percent.
"E0=0.0 mV": value of electric potential at the isopotencial point system.
Both values are defined after the calibration of equipment.
Finally it comes into potential measurement mode and shows "0 mV" and the last pro-
grammed temperature.
The equipment is ready for use.
Note: we recommend waiting 30 minutes. for stabilization of the pH-meter before pro-
ceeding to make measurements.
System operates following this diagram:
Screen shows last programmed values of the
slope and of E0
Button TEMP.
Temperature
selection
Button SLOPE.
6. CALIBRATION
Calibration can be made by:
Automatic detection of standar buffer solutions (4.00 pH, 6.86 pH y 9.18 pH) or manual
adjustment with different buffer solutions.
One or two points of calibration.
Note: clean very well the electrode before its calibration because resulting measure-
ments, based on the calibration of a dirty electrode will be wrong. Be sure the used buffer
sample for the standardization of the pH-meter is in good conditions.
Version 3 August 09
On
Button pH/mV
Measurement
Measuring
nts pH/mV
Button STD.
Calibration
Instruction manual 50903000
ENGLISH
Calibration at a point
It is used when it is not necessary to make precise measurements.
Prepare the standard buffer solution pH=6.86
Select measurement mode of pH by botton pH/mV (2.1)
Clean the electrode with distilled water and submerge in the solution
Measure the temperature of the buffer solution with a thermometer using button
"TEMP" (2.2) adjust the temperature on the screen with the temperature of the buffer
solution (ej. 25ºC).
Press button "STD" (2.4) (indicative "Std yes" on the screen) and after "ENTER" (2.5).
The pH-meter detects automatically the present standard solution and it shows its pH
value and selected temperature.
If you used a different buffer solution, please adjust by button STD (▲/▼) (2.4), the pH
value on the screen to the value of pH solution to the working temperature.
Note: to know this pH, look up Temperature-pH table that it is included in the back of
the envelopes of the buffer.
Press button "ENTER" (2.5); screen indicates "Std ok" and shows the slope value and
potential E0 are automatically recorded until next calibration. Finally it returns fo pH
measurement mode.
Wash the electrode with distilled water and dry it with filter paper or cellulose.
Note: after calibration, the system records new reference data and automatically dele-
tes the previous calibration data, the equipment is tested for its use.
The slope for the calibration at a point is considered by default 100.0%
Calibration at two points
Generally it is used to calibrate the slope of the electrode
Prepare standar buffer solutions pH=4.00 and pH=9.18.
Proceed to make the calibration with the solution pH=4.00 following steps 2. to 5. of
"Calibration at one point".
Press button "ENTER" (2.5); pH-meter returns to pH measurement mode.
Wash the electrode with distilled water and dry it with filter paper or cellulose.
Submerge the electrode in the solution pH=9.18.
Measure the temperature of buffer solution with a thermometer using "TEMP" button
Page 23 Page 24 Instruction manual 50903000
ENGLISH
Version 3 August-09